1. Field of the Invention
The present invention relates to a method and device of generating color data for color image formation by converting image data of three colors of cyan, magenta, and yellow, representing a color image to be formed, into color data for four colors including cyan, magenta, and yellow, and black.
2. Description of Related Art
Conventional color image forming devices such as printers and copy machines generally form color images on a recording paper using ink or toner of the four colors of cyan (C), magenta (M), yellow (Y), and black (K),
In this image forming process, a computer or scanner, for example, inputs image data that includes color data for the three colors of red (R), green (G), and blue (3) into the color image forming device. The image forming device then converts this image data to image data of the three colors of cyan (C), magenta (M), and yellow (Y). The image forming device then converts a portion of or all overlapping portions in which the three-color data overlap into black (K) data, thereby generating four-color data for color image formation.
For example, as shown in FIG. 1, a color data generating device 21 in this type of color image forming device can include a selecting unit 22 for selecting, as black data K, the minimum value among color data C1 (cyan), M1 (magenta), and Y1 (yellow); and a subtracter 23 for correcting each color data C1, M1, and Y1 by subtracting the black data K from each color data C1, M1, and Y1. The color data generating device 21 outputs the black data K, which is outputted from the selecting unit 22, and the color data C2, M2, and Y2 corrected by the subtracter 23 as the color data (C2, M2, Y2, K) for color image formation.
The generated color data C2, M2, Y2, and K is used to determine the amount of ink or toner for each color used in forming the color image.